1. Field of the Invention
This invention relates to a double-walled rotary tubular conveyor having a stabilizing drive means. A series of such stabilized conveyors can be employed as the drive mechanism for a driven conveyor of unlimited length.
2. Description of the Prior Art
There are currently four basic methods and structures for moving large masses of dry, semi-dry or viscous products from one place to another. These four basic structures are: conveyor belts, bucket loaders or scoop systems, screw feeders and vacuum systems. Each of those systems, however, have drawbacks which make them unsuitable for many applications.
Tubular conveyors are relatively uncommon, however, there is some literature on the subject. Typical tubular or closed belt conveyor approaches are discussed in the following U.S. Pat. Nos. 3,358,812; 3,332,537; 2,839,181; 2,212,024 and 2,108,488.
Each of the above patents disclose a closed tube of circular or rectangular cross-section having a longitudinal seam (i.e. along the direction of motion) which can be open and closed for loading and unloading. While the structures shown in the above patents are workable, the structures are relatively complex and the conveyor belts or tubes must be relatively resilient and the weight of material transported is limited by the relative strength of the tube along the longitudinal slit.
The most relevant prior art appears to be that disclosed in U.S. Pat. No. 4,174,033 issued on Nov. 13, 1979 to Ronald Parsons, the inventor of the present device. That patent discloses a true double-walled rotary tubular conveyor in which a hollow sleeve continuously turns inside out to convey material from one end to another. It describes what is believed to be the first effective attempt to unlock the motion necessary to accomplish a continuous tubular conveyor. There were, however, some short comings in the earlier structure disclosed in U.S. Pat. No. 4,174,033. One problem was that it was difficult to prevent the tube from moving forward or backwards or sideways under the influence of the drive wheels. Another problem was that there was no practical way of extending the conveyor system without placing the conveyor tubes in an abutting relationship. That approach was unacceptable because material tends to fall into or through the gaps between successive conveyors. Additionally, the prior art rotary tubular conveyor disclosed in U.S. Pat. No. 4,174,033 was acceptable for some straight line applications but was not effective for angled applications.